A method of this type is disclosed in German patent application DE 196 09 192 A1, for example. In the prior art method, the pressure introduced into the master brake cylinder is compared to a preset pressure signal and, subsequently, generates an output quantity in the form of a control current by which the electromagnet is actuated.
While a pressure-maintaining phase is performed irrespective of the vehicle operator's will, the introduced pressure must be corrected after a certain time in order to minimize the difference that occurred between the predetermined pressure and the pressure introduced into the master cylinder, said difference being caused by leakage of the brake booster, for example. It is considered less advantageous that in the prior art method the control current of the electromagnet stays on a level that brings the coil of the electromagnet to the load limit and, hence, jeopardizes the reliability of operation of the brake booster.